Incandescent lamp cap for edison holders



April 1934! H. c. GHVsEN I 1,955,629

INCANDESCENT LAMP CAP FOR EDISQN HOLDERS Filed Feb. 24, 1931 Patented Apr. 17, I934 PATENT OFFlCE INCANDESCENT LAlVIP CAP FOR EDISON HOLDERS Huibert Cornelis Ghysen, Middelburg, Netherlands, assignor to N V. The Vitrite Works,

Mid'delburg, Netherlands, a Dutch company of the Netherlands Application February 24, 1931, Serial No. 517,964 In the Netherlands February 25, 1930 v 4 Claims.

-It is an object of this invention to provide an improved cap fitting for incandescent electric lamps, more particularly, a cap suitable for insertion in holders or sockets of the Edison type.

In recent' times the requirements as regards safety in these lamp caps have become morestringent and consequently the height of that part of the cap which is situated between the upper or outer end of the screw thread and the insulation for the central contact has been made smaller. As the reduced height diminishes the doming of the contour in this region the resistance of the cap to endwise pressure tending to collapse it in the axial direction, has become considerably less. As insulating material between the central contact disc and the main shell of the cap black glass of a particular composition is employed and, since about 1902 these lamp caps have mostly been made on the well known machine of Alfred 2o Swan.

With this machine these lamp caps could be mass produced in a satisfactory manner and when the central contact discs and the shells were fed in automatically the way was opened for production of the lamp caps by entirely automatic means with a very large output per hour.

Since, when the Swan machine is used, the glass is poured in a molten and very fluid state into the shells and then subjected to pressure in the machine, the domed portion becomes highly heated. The result of this increase in temperature is that the brass becomes soft at this part and, therefore, can no longer oifer any great amount of resistance in the direction of the axis of the shell.

It is however important that the distance of the central contact disc from the commencement of the screw on the shell be as small as possible, so that for a lamp cap of a given overall length the screw thread shall extend as far along that length as possible. This is desirable in order that the lamp may screw firmly into its socket and may not work loose by reason of vibration. The so-called safety contact fittings which are coming more and more into general use and in which the lamp can only contact with current carrying parts when it is almost completely screwed home into the fitting, are so constructed that they will only receive lamp caps in which the distance of the central contact disc from the commencement of the screw on the shell is as small as possible.

The present invention enables the lamp cap to be produced automatically in the Swan ma- .chine, notwithstanding the fact that a high factor of resistance in an axial direction is maintained. The heating of the shell has now no longer any appreciable influence on the ability of the cap to withstand compression in an axial direction. The result achieved with the new shell is a surprising one and must be ascribed, in part, to the favourable action of the ribs or bulges as regards the cooling efiect obtained. By the presence of the ribs or bulges a greater superficial area of material is produced at this part and, consequently, better cooling of the shell at the part where it is most highly heated. The particular part in question will, therefore, not be heated to so high a temperature as in lamp caps not provided with ribs or bulges and, consequently the new caps will retain a high factor of resistance to compression. It follows from the foregoing remarks that, by means of solution effected by this invention, a high resistance factor to compression in an axial direction can be retained.

The above mentioned ribs, grooves or other reinforcements may conveniently be stamped out in the appropriate part of the lamp cap, for which purpose a die and a matrix of suitable construction are used. The ribs or grooves may also be formed in other ways, as, for example, by rolling the lamp cap under pressure, with the part to be treated over a surface provided with hollows or ribs.

Fig. 1 is a view of a constructional example of a lamp cap according to the present invention, Fig. 2 is a plan view of the cap shown in Fig. 1, Fig. 3 shows a modified construction and Fig. 4 a plan View of the same. Figs. 5 and 6 show a further constructional example of the subject matter of the invention.

In Fig. 1 the incandescent lamp cap as a whole is designated by the numeral 1. Numeral 2 denotes the central contact of the cap, 3 is the insulating material and 4 the screw thread. The substantially domed part of the lamp cap, between the upper end of the screw thread and the insulating material, is furnished with radially extending ribs or grooves 5, which are produced by rods. These ribs increase, in a considerable degree, the resistance factor to pressure applied in an axial direction and prevent the domed part of the lamp cap from being crushed in or otherwise deformed when the lamp is screwed into the fitting.

' In the construction shown in Figs. 3 and 4 the lamp cap is reinforced by strengthening the domed part thereof with hollows 6 stamped therein instead of using the ribs or grooves shown in Figs. 1 and 2.

Figs. 5 and 6 shows a further possible form of construction. The domed part between the outer screw threaded end of the cap and the insulating material is in this case, simply made of corrugated form as shown at '7. The manufacture of this modification is likewise carried out by simple pressing. At the top of the domed portion is an adjoining bezel 7 which partially surrounds the insulating material and holds it securely in the lamp cap.

What I claim is:

1. An incandescent lamp cap comprising a threaded cylindrical body portion, a domeshaped portion formed of metal continuing therefrom, an insulating element supported by the dome-shaped portion, a contact cap on the outer end of the insulating element and a circular series of radially extending grooves formed on the outer surface of the dome-shaped portion for reinforcing the latter.

2. An incandescent lamp cap comprising a threaded cylindrical body portion formed of metal, a dome-shaped portion continuing therefrom,

an insulating element supported by the domeshaped portion, a contact cap on the outer end of the insulating element, and a circular series of sockets depressed in the outer surface of the dome-shaped portion for reinforcing the same.

3. Anincandescent lamp comprising a threaded cylindrical body portion formed of metal, a metallic dome-shaped portion continuing therefrom, an insulating element supported by the dome-shaped portion, a contact cap on the outer end of the insulating element, and a circular series of reinforcing elements formed on the outer surface of the dome-shaped portion.

4. An incandescent lamp cap comprising a threaded cylindrical body formed of sheet metal, a dome-shapedportion continuing therefrom, an insulating element supported by the dome-shaped element, a contact cap on the outer end of the insulating element, and a circular series of raised radially disposed ribs formed on the outer surface of the dome-shaped portion for reinforcing the same.

HUIBERT CORNELIS GHYSEN. 

